Electronic computers of both the digital and the analogue varieties have made possible many studies with the use of mathematical models of physiological systems. This area of biomathematics has grown rapidly in the last decade. The general aims, limitations, and problems of such mathematical models are reviewed in this paper. Techniques for the conformation of such mathematical models to experimental data by the application of electronic computers are discussed. Finally, three specific examples are presented briefly: the regulation of the concentration of glucose in the blood, the metabolism o f calcium by bone, and the stimulation of mitochondrial respiration. These examples are presented, rather than an encyclopedic list o f uses or a technical set o f computer programs, in the hope that they will better illustrate some o f the applications o f electronic computers in biomathematics.